Dec. 13 (UPI) -- Missing text messages from fired FBI agent Peter Strzok and bureau lawyer Lisa Page were permanently erased when their devices were turned in, a new report from the inspector general said Thursday.

The federal watchdog said in the report it found "no discernible patterns" about the content of thousands of messages the FBI was able to recover between Strzok and Page. Both have been part of special counsel Robert Mueller's investigation of Russia, and were romantically involved when they sent the messages in 2016. Strzok, in fact, was a member of Mueller's investigative team.

The Justice Department's Office of the Inspector General detailed how it recovered some of the lost messages. The report said the messages contained a mix of "some political content, some work-related content and some personal content."

President Donald Trump has repeatedly criticized Strzok's conduct during the sensitive Mueller investigation and said it shows political bias. Some of the messages indicated neither Strzok nor Page were supporters of Trump's election.

Mueller's office at the time was investigating whether former secretary of state and then-presidential candidate Hillary Clinton improperly used a private email account while she was in former President Barack Obama's Cabinet. Strzok, a senior counter intelligence agent, was assigned to the case and Page was involved as well. They were assigned to investigate potential Russian interference in the 2016 presidential election. Strzok was ultimately fired.

Thursday's report said the FBI used special software to collect more than 20,000 text messages from the pair's phones, but not all were sent between Strzok and Page. Investigators have already released some of the controversial texts, including a message from Strzok saying he would "stop" President Donald Trump from winning the election.

Missing text messages from the pair's iPhones, though, continue to elude the FBI.

The FBI attempted to recover the text messages during the time that Strzok and Page were working on the Mueller probe, but the government-issued iPhones had been wiped clean. Strzok's device had been given to another agent after he was fired and Page's was recovered months later, but had been reset -- a process that wipes all data from the phone and returns it to its factory condition.

Early this year, the Office of the Inspector General contacted Verizon Wireless to determine if the carrier retains old text messages. Verizon said messages are retained for up to seven days after they are sent, and then erased. The missing messages in question were much older than a week by that time and Verizon no longer had them.